1. Field of Invention
The present invention relates to a touch panel. More particularly, the present invention relates to a controlling method and a touch panel in which a base capacitance of a panel capacitor is equivalently decreased.
2. Description of Related Art
With the rapid development of technology, electronic devices such as notebooks, mobile phones or portable multimedia players usually adopt touch panels as a human-machine interface. The touch panels are generally categorized into capacitive touch panels and resistive touch panels. The capacitive touch panels are operated by approaching or touching the touch panels with a finger or a conductive material to change capacitances of the touch panels. When the variation in capacitances is detected, the approached or touched location can be identified to further execute a predetermined operation corresponding to the foregoing approached or touched location.
FIG. 1 illustrates a conventional touch panel. As shown in FIG. 1, a conventional touch panel includes a plurality of panel capacitors (e.g. panel capacitors C11-C15), and the panel capacitors are disposed at the intersections of the columns X1˜X8 and the rows Y1˜Y8. The touch panel scans the panel capacities on the rows and the columns to obtain the capacitances of the panel capacitors. Every capacitance includes two parts, in which the first part is a base capacitance representing a capacitance without touching, and the second part is a capacitance variance generated by a touch.
In general, a signal corresponding to the capacitance will be converted into digital data by an analog digital converter (ADC). Obtaining the capacitances at different time points and calculating the variance of the capacitances can acquire a touched position. However, a resolution of the ADC is required to be high when the base capacitance is large and the capacitance variance is relatively small. For example, if the base capacitance is 21.4 pF, the capacitance variance is 0.1 pF, and the capacitance variance is quantized into 256 levels, then the ADC has to recognize X levels, in which 256/X=0.1/21.4 (i.e. X=54784) so that the ADC is required to have 16 bits of resolution. Therefore, how to decrease a resolution requirement of the ADC is an issue concerned by people skilled in the art.